A Collision that Shook the Space Community

It's hard to believe that twenty years have gone by since NASA's DART mission collided with a satellite after an unexpected fuel crisis during its rendezvous attempt.

What Was DART Really Meant to Do?

The Demonstration for Autonomous Rendezvous Technology, or DART, was crafted to demonstrate cutting-edge satellite rendezvous capabilities—not to be confused with the later triumphant Double Asteroid Redirection Test that successfully impacted Dimorphos in 2023. DART was designed to merge with the MUBLCOM satellite in Earth's orbit.

Fuel Frenzy Leads to Collision

In a twist of fate, the mission turned disastrous when unexpected fuel consumption spiraled out of control. Rather than smoothly rendezvousing, the spacecraft ran out of maneuvering fuel and slowly collided with its target, leading to a planned retirement burn for its deorbit.

Budget Overruns and Last-Minute Adjustments

Originally budgeted at $47 million, the project ballooned to a staggering $110 million, and what was supposed to be a swift 24-hour mission turned into a cautionary tale. Launched by a Pegasus rocket, DART was set to park beneath MUBLCOM and use its Hydrazine Auxiliary Propulsion System to maneuver into position.

As the Plan Unraveled

Initially, everything seemed to be going as scheduled. DART positioned itself 40 km behind and 7.5 km below its target. However, mission controllers soon discovered alarming discrepancies with the spacecraft's navigation system. As DART advanced within 200-500 meters of MUBLCOM, it became increasingly clear that the fuel supply would not last.

Software Errors at the Heart of the Mishap

DART’s inability to process commands from ground control compounded the issues. Faulty software produced incorrect navigational data, triggering constant resets and excessive thruster uses. The situation escalated until DART unintentionally targeted MUBLCOM without the capability to stabilize its approach.

The Collision: A Close Call

During the impending crash, DART was hurtling towards MUBLCOM at 1.5 meters per second, while its system inaccurately reported a distance of 130 meters, causing it to believe it was retreating.

Last-Ditch Efforts and Aftermath

DART's collision avoidance system activated one minute and twenty-three seconds before impact, but the flawed perception of distance and velocity rendered it futile. A mere three minutes and forty-nine seconds after the collision, DART initiated its deorbit sequence.

Unexpected Survivors of the Collision

Remarkably, both satellites endured the encounter. MUBLCOM, launched in 1999 for DARPA, had completed its mission and even benefited from the impact, as it was pushed to a higher orbit. DART, unfortunately, re-entered Earth's atmosphere in 2016.

Lessons Learned

Though some may view DART's mission as a failure, it provided invaluable lessons in software validation and engineering design flaws. What was initially considered a vital part of the Orbital Space Plane program continued to hold significance for NASA, leading to the development of autonomous capabilities for cargo delivery and International Space Station (ISS) operations.